Miniature cryogenic pump method and apparatus for ion lasers

Abstract

A method and apparatus for reducing gas pressure in a laser wherein a miniature cryogenic pump is constructed to comprise an integral part of a laser plasma tube. The pump includes a container which holds molecular sieve material, a conduit which permits communication between the container and the plasma tube, and a valve which controls the communication along the conduit. All connections between the container, conduit, valve and plasma tube are gas-tight so as to maintain the ion integrity of the plasma tube with respect to the atmosphere. In operation, a service engineer immerses the container in a refrigerant, such as liquid nitrogen, and opens the valve until the pressure in the plasma tube reaches the desired level. Thereafter the valve is closed and the container permitted to return to ambient temperature. Further in accordance with the present invention, means are provided for preventing over pressure in the container. In the event that other gases are introduced into the container due to leaks in the pump or plasma tube, a puncturing pin is positioned in relation to a diaphragm, which diaphragm expands into contact with the puncturing pin when there is an over pressure condition in the container.

I claim: 
     
       1. An apparatus for reducing gas pressure in a gas tight laser system of the type including a plasma tube which contains a volume of lasing gas at a gas pressure, comprising molecular sieve material cryogenically cooled to a temperature such that said sieve material traps said lasing gas thereby producing a pumping action which draws said lasing gas from said plasma tube;   means for containing the molecular sieve material;   conduit means connecting the plasma tube and the containing means for permitting communication between the interior of the plasma tube and the interior of the containing means; and   means coupled to the conduit means for regulating communication along the conduit means, wherein the plasma tube, the containing means, the conduit means and the regulating means form an integral structure which is sealed to the atmosphere.   
     
     
       2. The apparatus of claim 1 wherein the regulating means include a bellows valve. 
     
     
       3. The apparatus of claim 1 wherein the regulating means include a valve. 
     
     
       4. The apparatus of claim 3 wherein the valve is manually operable. 
     
     
       5. The apparatus of claim 1 wherein at least a portion of the conduit means comprise flexible tubing. 
     
     
       6. The apparatus of claim 1 wherein the molecular sieve material includes porous zeolite. 
     
     
       7. The apparatus of claim 1 wherein the containing means include a body which defines a chamber, wherein the molecular sieve material is positioned in the chamber and the body has a port which opens into the chamber, and further wherein the conduit means are coupled to the port.   
     
     
       8. The apparatus of claim 7 further including filter means positioned at the port of the body for retaining the molecular sieve material within the chamber. 
     
     
       9. The apparatus of claim 8 wherein the filter means is a screen. 
     
     
       10. The apparatus of claim 7 wherein the body further includes a diaphragm portion which is deformable; and   a cylindrical pin having one end which is conically shaped and ends in a point, wherein said cylindrical pin includes an axial bore extending partially into the pin and a transverse bore which extends radially through the cylindrical pin and in communication with the axial bore, and further wherein said cylindrical pin is positioned in a housing which is coupled to the body so that said housing and body form an air tight chamber but for the passage way defined by the radial and axial bores in the cylindrical pin.   
     
     
       11. An apparatus for reducing gas pressure in a gas tight laser system of the type including a plasma tube which contains a volume of gas at a gas pressure, comprising molecular sieve material cryogenically cooled to a temperature such that said sieve material traps said lasing gas thereby producing a pumping action which draws said lasing gas from said plasma tube; means for containing the molecular sieve material, wherein the containing means include a body which defines a chamber, wherein the molecular sieve material is positioned in the chamber and the body has a port which opens into the chamber, and further wherein conduit means are coupled to the port; and wherein the body includes a portion which is deformable above a predetermined pressure, and further including means positioned adjacent the deformable portion for puncturing the deformable portion when said portion deforms a predetermined amount;       conduit means connecting the plasma tube and the containing means for permitting communication between the interior of the plasma tube and the interior of the containing means; and   means coupled to the conduit means for regulating communication along the conduit means, wherein the plasma tube, the containing means, the conduit means and the regulating means form an integral structure which is sealed to the atmosphere.   
     
     
       12. The apparatus of claim 11 wherein the puncturing means comprise an elongate member having a pointed end wherein said elongate member is positioned in fixed relation to the body and with pointed end abutting against the deformable portion. 
     
     
       13. A method for reducing gas pressure in a gas tight laser system of the type including a plasma tube which contains a volume of lasing gas at a gas pressure comprising the steps of confining cryagenically cooled molecular sieve material in a container;   coupling the container to the plasma tube so that the container forms an integral part of the gas tight laser system which is sealed to the atmosphere and so that the molecular sieve material is in communication with the plasma tube;   refrigerating the container so that said molecular sieve material operates as a cryogenic pump thereby producing a pumping action which draws said lasing gas from said plasma tube; and   controlling communication between the container and the plasma tube so that the gas pressure in the plasma tube achieves a desired level.   
     
     
       14. The method of claim 13 wherein the coupling step includes the step of positioning a bellows valve between the container and the plasma tube and the controlling step includes the step of operating the bellows valve between a closed and an open position to alternatively block and permit communication between the container and the plasma tube. 
     
     
       15. The method of claim 13 wherein the refrigerating step includes the step of immersing the container in liquid nitrogen. 
     
     
       16. The method of claim 13 further including the step of providing means for releasing excessive pressure in the container. 
     
     
       17. An improved laser system of the type including a plasma tube which contains a volume of lasing gas at a gas pressure, means for exciting the plasma tube so that a discharge is generated from the plasma tube, and means for resonating the discharge from the plasma tube, the improvement comprising pump means integrally coupled to the plasma tube for pumping the lasing gas from the plasma tube said pump means including   molecular sieve material cryogenically cooled to a temperature such that said sieve material traps said lasing gas thereby producing a pumping action which draws said lasing gas from said plasma tube;   means for containing the molecular sieve material;   conduit means connecting the plasma tube and the containing means for permitting communication between the interior of the plasma tube and the interior of the containing means; and   means coupled to the conduit means for regulating communication along the conduit means, wherein the plasma tube, the containing means, the conduit means and the regulating means form an integral structure which is sealed to the atmosphere.